To provide a hydraulic differential that allows for reasonable manufacturing tolerances by avoiding large hydraulic thrust forces between variable displacement and fixed displacement hydraulic units.

The hydraulic differential 2 has a variable displacement hydraulic unit 4 of the axial piston type, a fixed displacement hydraulic unit 6 of the axial piston type, a stationary housing 24 for mounting the hydraulic units, an input shaft for coupling to a variable speed power source, and an output shaft for coupling to a constant speed load. The hydraulic differential comprises: a wobbler and a port plate for the variable displacement hydraulic unit coupled to the stationary housing; an axial block and piston set for the variable displacement hydraulic unit, a port plate for the fixed displacement hydraulic unit and a wobbler for the fixed displacement hydraulic unit coupled to the input shaft; and an axial block and piston set for the fixed displacement hydraulic unit coupled to the output shaft. The variable displacement hydraulic unit port plate and the fixed displacement hydraulic unit port plate are coupled to each other through a circumferential interface to minimise hydraulic thrust forces developed by the hydraulic units.